For example, in a copier, a drum-shaped photoreceptor is uniformly charged and then exposed to light controlled on the basis of image information to form an electrostatic latent image (toner) on the photoreceptor, and using an image-fixing device, the toner is transferred in an unfixed state to a recording medium such as a piece of paper, and then fixed to the recording medium by heating and pressurization.
For example, Patent Document 1 discloses an image-fixing device including: a pressure roller rotatably provided; and a cylindrical endless belt rotatably provided, which is pressed by the pressure roller. A pressure member is provided inside the endless belt so as to press the endless belt toward the pressure roller side. A porous resin member (sliding member) containing a lubricant is provided between the pressure member and the endless belt, and serves to rotate the endless belt smoothly.
As an example of the material to be used for sliding members, Patent Document 2 discloses the use of a fabric woven with a porous yarn. In Patent Document 2, there are used porous PTFE fibers produced by an expanding method, and the method disclosed in Patent Document 3 is exemplified as the method of producing the porous PTFE fibers by an expanding method.
Patent Document 3 discloses three methods as the main methods of obtaining a PTFE yarn-like product. That is, the first method is the emulsion spinning method in which a PTFE dispersion, or a composite solution of a PTFE dispersion and a matrix polymer such as alginic acid and viscose, is discharged into a coagulating bath such as an aqueous sulfuric acid solution. The second method is the slit yarn method in which a slit tape of expanded porous PTFE obtained by expanding an extrudate of a PTFE fine powder-containing paste after the removal of an extrusion aid is expanded again into a yarn shape. The third method is the solution spinning method in which a yarn is spun by extruding a solution of PTFE in a perfluorocarbon compound solvent through a spinneret into an inert gas or an inert liquid.
The yarns used in Patent Documents 2 and 3 are so-called single yarns (monofilaments), and the lubricant fed to cause the woven fabric to function as the sliding member is retained in the space between the yarns of the woven fabric.